General Key to Families 11 



6B. Perianth absent Fam. 34. Potamogetonaceae, 120 



5B. Carpel 1, or if more than 1, united into a compound ovary. 

 8A. Perianth-segments absent or much reduced. 



9A. Marine aquatics; leaves ribbonlike; flowers unisexual, lateral in the inflorescence Fam. 36. Zosteraceae, 124 



9B. Terrestrial or fresh-water aquatics. 



lOA. Free-floating gregarious stemless aquatics, with leaves and roots only Fam. 45. Lemnaceae, 264 



lOB. Aquatic or in wet places but not free-floating, with stems and leaves (sometimes these much reduced). 

 1 lA. Leaves linear or threadlike, entire or denticulate, frequendy with stipules; plants submerged. 



Fam. 35. Najadaceae, 123 

 IIB. Leaves broader; plants terrestrial or growing in water but never submerged. 

 12A. Flowers not in a spadix enclosed in a spatlie. 



13A. Inflorescence consisting of unisexual heads or spikes without involucral bracts. 



14A. Leaves 2-ranked; flowers very numerous in congested elongate spikes Fam. 32. Typhaceae, 118 



14B. Leaves 3-ranked; flowers in congested globose clusters Fam. 33. Sparganiaceae, 118 



13B. Inflorescence in solitary, bisexual, globose to hemispherical heads surrounded by involucral bracts. 



Fam. 46. Eriocaulaceae, 265 



12B. Flowers arranged on a spadix enclosed in a spathe Fam. 44. Araceae, 255 



8B. Perianth-segments sepallike or petallike. 



15A. Plants treelike, relatively woody; leaves large, rigid, evergreen, palmately or pinnately compound. 



Fam. 43. Palmae, 253 

 15B. Plants herbaceous; leaves typically simple, not large. 

 16A. Perianth-segments sepallike or glumelike. 



17A. Perianth-segments glumelike Fam. 50. Juncaceae, 273 



17B. Perianth-segments sepallike Fam. 37. Scheuchzeriaceae, 125 



16B. Perianth-segments, at least the inner ones, typically petallike. 

 18 A. Stamens 3 or 6 or fewer by abortion. 



19A. Leaves with a basal membranous closed sheath; perianth very distinctly 2-seriate, the outer scpallike, the 



inner corollalike Fam. 47. Commelinaceae, 270 



19B. Leaves without basal membranous sheaths; perianth mostly corollalike, the 2 series alike or nearly so. 



20A. Inflorescence subtended by a spathelike leaf-sheath Fam. 48. Pontederiaceae, 272 



20B. Inflorescence not subtended by a spathelike leaf-sheath Fam. 52. Liliaceae, 279 



18B. Stamens 4 or 1. 



21A. Flowers actinomorphic; stamens 4, with a long protruding connective Fam. 51. Stemonaceae, 278 



21B. Flowers zygomorphic; stamen 1, without a protruding connective Fam. 49. Philydraceae, 272 



4B. Ovary wholly inferior. 



22 A. Plants aquatic Fam. 39. Hydrocharitaceae, 128 



22B. Plants mostly terrestrial. 



23A. Scandent herbs; flowers unisexual Fam. 54. Dioscoreaceae, 313 



23B. Erect herbs; flowers bisexual. 

 24A. Fertile stamens 3 or 6. 



25A. Stamens 6 Fam. 53. Amaryllidaceae, 311 



25B. Stamens 3 Fam. 55. Iridaceae, 315 



24B. Fertile stamens 1 or 2. 



26A. Stamens and pistil distinct Fam. 56. Zingiberaceae, 316 



26B. Stamens 1 or 2, fused to the style Fam. 58. Orchidaceae, 319 



IB. Plants saprophytic, leafless, or the leaves without chlorophyll. 

 27A. Ovary superior or nearly so. 



28A. Flowers unisexual; carpels many and free, 1-locular and 1-ovuled Fam. 40. Triuridaceae, 130 



28B. Flowers bisexual; carpels 3, connate at least toward the base; ovules many Fam. 52. Liliaceae (Protolirion), 279 



27B. Ovary inferior. 



29A. Flowers actinomorphic; stamens 3, distinct Fam. 57. Burmanniaceae, 318 



29B. Flowers zygomorphic; fertile stamens 1 or 2, fused to the style Fam. 58. Orchidaceae, 319 



Subclass 2. Dicotyledoneae 



Leaves mostly net-veined; flowers typically 5-merous but variously modified, rarely 3- or 6-merous. 



lA. Corolla absent or rudimentary; calyx rarely petallike, sometimes none. 

 2A. Flowers perfect or unisexual, borne in aments; trees or shrubs. 

 3A. Flowers of both sexes in aments. 



4A. Capsules many-seeded; seeds provided with a tuft of long hairs Fam. 62. Salicaceae, 361 



4B. Fruit 1 -seeded, without a tuft of hairs. 



5A. Female flowers solitary in axils of bracts Fam. 63. Myricaceae, 369 



5B. Female flowers 2 or 3 in axils of bracts Fam. 65. Bctulaceae, 370 



3B. Flowers of only one sex (staminate) in aments. 



6A. Ovary superior; fruit an achene sometimes imbedded in the fleshy or juicy calyx Fam. 68. Moraceae, 382 



6B. Ovary inferior; fruit a nut, sometimes drupelike. 



7A. Lrcaves pinnately compound Fam. 64. Juglandaccae, 369 



